Module progress 

Execution phases and small progress-related contracts.

Responsibilities:

• Define ExecutionPhase, a stable enum used across run history and ETA estimation.
• Provide small, display-oriented helpers (phase name/number/icon) without owning rendering.

Not handled here:

• Rendering progress bars/spinners (CLI or GUI).
• Persisting execution history (see crate::execution_history).
• ETA heuristics (see crate::eta_calculator).

Invariants/assumptions:

• Phase numbering is stable: planning=1, implementation=2, review=3, complete=0.
• Serialization format is snake_case for stable on-disk contracts.

Enums

ExecutionPhase

Execution phases for multi-phase task workflows.